Plant for manufacturing cement clinker

ABSTRACT

Described is a plant for manufacturing cement clinker comprising a preheater ( 1 ) which comprises at least one last cyclone ( 1   d ) and at least one next-to-last cyclone ( 1   c ) which is connected in series via a gas duct ( 2   c ) to and fed with a gas from the last cyclone ( 1   d ), a calciner ( 3 ) which comprises at least one inlet opening ( 9 ) for introducing preheated raw meal from the last cyclone ( 1   d ), and which is connected to a subsequent separating cyclone ( 4 ), a gas duct ( 2   d ) which connects the separating cyclone ( 4 ) to the last cyclone ( 1   d ), and which comprises at least one inlet opening ( 11 ) for introducing preheated raw meal from the next-to-last cyclone ( 1   c ). The plant is peculiar in that the inlet opening ( 11 ) for introducing preheated raw meal from the next-to-last cyclone ( 1   c ) into the gas duct ( 2   d ) which connects the separating cyclone ( 4 ) to the last cyclone ( 1   d ) in a vertical plane is located under at least one inlet opening ( 9 ) for introducing preheated raw meal from the last cyclone ( 1   d ) into the calciner. Hence, without affecting the installation height of the preheater, it will be possible to locate the last cyclone ( 1   d ) of the preheater ( 1 ) at an arbitrary height relative to the calciner ( 3 ), and preheated raw meal from the last cyclone ( 1   d ) can therefore be introduced at any point into the calciner ( 3 ) without any use of lifting equipment.

The present invention relates to a plant for manufacturing cementclinker comprising a preheater which comprises at least one last cycloneand at least one next-to-last cyclone which is connected in series via agas duct to and fed with gas from the last cyclone, a calciner whichcomprises at least one inlet opening for introducing preheated raw mealfrom the last cyclone, and which is connected to a subsequent separatingcyclone, a gas duct which connects the separating cyclone to the lastcyclone, and which comprises at least one inlet opening for introducingpreheated raw meal from the next-to-last cyclone.

Plants of the aforementioned kind for manufacturing cement are known forexample from DE 19649922 and DE 19524649. In these known plants, rawmeal is introduced from a mill plant, typically into the gas inlet ductof the first cyclone of the cyclone preheater and the raw meal ispreheated as it is led through the cyclones of the preheater incounterflow to a hot gas flow, typically hot exit gases from thesubsequent calciner and/or a subsequent kiln. The preheated raw meal isextracted from the last cyclone of the preheater and introduced into thecalciner for calcination therein. The calciners described in theabove-mentioned patent specifications comprise a first upward-directedsection and a subsequent downward-directed section which is connected tothe separating cyclone of the calciner. According to the known plants,the preheated raw meal from the last cyclone of the preheater isintroduced into the lower end of the upward-directed section of thecalciner and, therefore, the last cyclone of the preheater is locatednext to the calciner due to the overall installation height of thepreheater. In instances where it is desirable to introduce preheated rawmeal at a higher intake point of the calciner, such raw meal musttherefore be extracted from the next-to-last cyclone of the preheater,which is disadvantageous since, because of the lower temperature in thelatter, this may result in poor heat economy and also an excessivereduction of the temperature in the calciner.

It is the objective of the present invention to provide a plant by meansof which sufficiently preheated raw meal from the last cyclone of thepreheater can be introduced into the upper end of the calciner withoutcausing the installation height of the preheater to be increased.

This is achived by a plant of the kind mentioned in the introduction andbeing characterized in that the inlet opening for introducing preheatedraw meal from the next-to-last cyclone into the gas duct which connectsthe separating cyclone to the last cyclone in a vertical plane islocated under at least one inlet opening for introducing preheated rawmeal from the last cyclone into the calciner.

Hence, without affecting the installation height of the preheater, itwill be possible to locate the last cyclone of the preheater at anarbitrary height relative to the calciner, and preheated raw meal fromthe last cyclone can therefore be introduced at any point into thecalciner without any use of lifting equipment.

It is preferred that the material outlet from the last cyclone of thepreheater in a vertical plane is located above the upper end of thecalciner.

In order to limit the installation height of the preheater, it ispreferred that the gas duct which connects the last and next-to-lastcyclone of the preheater comprises at least one downward-directed ductsection.

The invention will now be described in further details with reference todrawing where

FIG. 1 shows a first embodiment of a plant according to the invention,

FIG. 2 shows a second embodiment of a plant according to the invention,

FIG. 3 shows a third embodiment of a plant according to the invention,and

FIG. 4 shows a fourth embodiment of a plant according to the invention.

FIGS. 1 to 4 show examples of different kiln plants for manufacturingcement clinker. All the shown kiln plants are of the ILC-type, but theinvention may also be used in connection with plants of the SLC-type orother plants which are combinations of such plants.

All of the plants comprise a cyclone preheater 1 with four cyclones 1 a,1 b, 1 c and 1 d, where 1 a is the first cyclone, 1 b is the secondcyclone, 1 c is the third or next-to-last cyclone and 1 d is the fourthor last cyclone. The cyclones are connected in series and fed withgas/raw meal suspension via gas ducts 2 a, 2 b, 2 c and 2 d.

The plants also comprise a calciner 3 which comprises at least one inletopening 9 for introducing preheated raw meal from the last cyclone 1 dvia its material outlet 6, and being connected to a separating cyclone4, a rotary kiln 5 and a clinker cooler 7. The gas duct 2 d whichconnects the separating cyclone to the last cyclone, comprises at leastone inlet opening 11 for introducing preheated raw meal from thenext-to-last cyclone.

According to the invention it is a common feature of all the shownplants that the inlet opening 11 for introducing preheated raw meal fromthe next-to-last cyclone 1 c into the gas duct 2 d which connects theseparating cyclone 4 to the last cyclone 1 d in a vertical plane islocated under at least one inlet opening 9 for introducing preheated rawmeal from the last cyclone 1 d in the calciner 3.

The kiln plants shown in FIGS. 1 and 2 both comprise a calciner 3 whichis designed with a so-called swan's neck which in practice means thatthe calciner comprises a first upward-directed section 3 a, which via a180° bend 3 c is connected to a second downward-directed section 3 bwhich in turn is connected to the separating cyclone 4.

In the kiln plant shown in FIG. 1 the cyclone 1 d is made up of aconventional cyclone in which the gas/raw meal suspension is introducedtangentially into the upper end of the cyclone and in which theseparated raw meal is discharged through the material outlet 6, whilethe discharge duct 2 c for carrying the gas to the cyclone 1 c islocated at the top of the cyclone 1 d. In the shown embodiment the duct2 c comprises a downward-directed section 15 thereby allowing thecyclone 1 c in a vertical plane to be located at a lower level, makingit possible to reduce the installation height.

In the kiln plant shown in FIG. 2, the cyclone 1 d is made up of acyclone which corresponds to that shown in FIG. 1, except for the factthat the discharge duct 2 c for conveying the gas to the cyclone 1 cextends through the bottom. This embodiment also makes it possible forthe cyclone 1 c at a vertical plane to be located at a lower level.

The kiln plant shown in FIG. 3 corresponds to the plant shown in FIG. 1except for the fact that the calciner 3 is not designed with a swan'sneck and that the separating cyclone 4 is designed with a gas dischargeduct 2 d which extends through the bottom hereof.

The kiln plant shown in FIG. 4 comprises a calciner 3 in which exitgases from the kiln 5 and fuel are introduced into the upper end 21 ofthe calciner 3 and led down through the calciner 3 as a suspension.Preheated air from the clinker cooler 7 and preheated raw meal from thelast cyclone 1 d of the preheater 3 is introduced into the calciner 3 ata location further down on the calciner 3, thereby causing the preheatedair to be led down through the calciner 3, with the air being graduallymixed with the exit gas/fuel suspension, and with force of gravitycausing the raw meal to be led down through the calciner 3 along itswall. In the lower end 23 of the calciner the raw meal is againsuspended in the exit gases whereafter the formed exit gas/raw mealsuspension is extracted from the lower end 23 of the calciner 3 anddirected to the separating cyclone 4. From the separating cyclone 4 theexit gases are passed upward to the cyclone 1 d, which, in similarmanner as the embodiment shown in FIG. 1, is made up of a conventionalcyclone in which the exit gas/raw meal suspension is introducedtangentially into the upper end of the cyclone, and in which theseparated raw meal is discharged through the material outlet 6, whilethe discharge duct 2 c for carrying the gas to the cyclone 1 c islocated at the top of the cyclone 1 d. The duct 2 c comprises adownward-directed duct section 15 allowing the cyclone 1 c in a verticalplane to be located at a low level relative to the upper end of thecalciner so that the installation height can be reduced.

The present invention is not limited to the shown embodiments which areillustrative only, thus allowing for many different embodiments andcombinations of the shown embodiments which are within the scope thepresent invention.

1. Plant for manufacturing cement clinker comprising a preheater whichcomprises at least one last cyclone and at least one next-to-lastcyclone which is connected in series via a gas duct to and fed with gasfrom the last cyclone, a calciner which comprises at least one inletopening for introducing preheated raw meal from the last cyclone, andwhich is connected to a subsequent separating cyclone, a gas duct whichconnects the separating cyclone to the last cyclone, and which comprisesat least one inlet opening for introducing preheated raw meal from thenext-to-last cyclone, wherein the inlet opening for introducingpreheated raw meal from the next-to-last cyclone into the gas duct whichconnects the separating cyclone to the last cyclone in a vertical planeis located under at least one inlet opening for introducing is preheatedraw meal from the last cyclone into the calciner.
 2. Plant according toclaim 1, wherein the material outlet from the last cyclone of thepreheater in a vertical plane is located above the upper end of thecalciner.
 3. Plant according to claim 1, wherein the gas duct whichconnects the last and next-to-last cyclone of the preheater comprises atleast one downward-directed duct section.